The present invention relates to an arbor for mounting a tool to a spindle of a machine tool and a machining method of employing the same, and more particularly to an arbor for mounting a tool such as a drill or a grindstone to the end of a spindle of a machine tool and a machining method of employing such arbor.
In performing various cutting or grinding operations on workpiece, it is necessary to ensure the appropriate supply of a lubricant such as cutting fluid or grinding fluid to an area of machining to lubricate the tool and the workpiece and prevent seizure and wear of the tool as well as the removal by the lubricant of any chips resulting from such machining.
When, for example, a cup-shaped grindstone is used for a face grinding, it is essential to ensure the appropriate supply of a grinding fluid or lubricant to the area in which a considerably large amount of heat is generated, as the grindstone and the workpiece to be ground have a long arc of contact therebetween. No device or method that is satisfactory for that purpose has, however, been available as yet. According to the practice which has hitherto been performed, a cup-shaped grindstone 62 mounted to the end of a spindle 63 and the workpiece 64 are moved relative to each other and a lubricant is supplied thereto bY an external nozzle 61, as shown in FIG. 8. It has, however, been difficult to ensure the appropriate supply of the lubricant, as it is prevented by, for example, a layer of moving air which is formed by the rotatiOn Of the cup-shaped grindstone 62. The formation of a lubricant passageway in the head for the grindstone has, however, been a complicated work because of the limited space which it can afford. Moreover, in order to maintain the strength of the grindstone, the grindstone has certain limitations on its shape. The provision of any such passageway has, therefore, been possible only at a very high cost.
Other problems that have hitherto been encountered include the scattering of the lubricant from anY such passageway which occurs when the tool is removed from the tool mounting portion of the spindle.
On the other hand, when, for example, a drilling is performed by a core drill 74 as shown in FIG. 9(a), or a work of forming a groove is performed by a grindstone 75 attached to a shaft as shown in FIG. 9(b), it has been usually carried out by rotating the core drill 74 or the grindstone 75 supported on an arbor 73 fitted in a spindle, while supplying a lubricant from an external nozzle 71 to that part of a workpiece 72 which is worked on.
Other prior art includes an arrangement as shown in FIG. 10. A lubricant is supplied through a lubricant supply passage 81 formed in the housing 82 of a machine tool and a rotary joint 83 into an arbor 1 fitted in a spindle. The lubricant is supplied from the arbor 1 to a lubricant passage 84 in a tool T, and is discharged through the end of the tool T. In FIG. 10, reference numeral 8 denotes the spindle, and 6 denotes a collet.
According to the arrangement in which the external nozzle 71 is employed for supplying the lubricant from the outside of the core drill 74 or the grindstone 75, it has been impossible to achieve an effective supply of the lubricant to the area of machining, since the rotation of the core drill 74 or the grindstone 75 causes the scattering of the lubricant and the resultant layer of moving air prevents the appropriate supply of the lubricant.
According to the latter arrangement including the rotary joint 83, the lubricant is supplied from the lubricant supply passage 81 in the housing 82 which is not rotatable, to the arbor 1 through the rotary joint 83, and the lubricant is, therefore, not supplied to the tool T satisfactorily if the rotating speed of the tool T is increased. Accordingly, the tool T has only a limited rotating speed.